Sensorless speed measurement of induction machines using Short Time Fourier Transformation

Ssensorless speed measurement of induction machines using Short Time Fourier Transformation (STFT) is presented in this paper. The sensorless speed information of induction motors was derived from space vector angular fluctuation which is obtained from stator current by exploring the position of the current space vector in the space vector plane. By applying STFT to the space vector angular fluctuation signals, the eccentricity associated motor speed information can be extracted. Interpolation technique has been used to improve the accuracy of the STFT. The method has been verified on an ABB 2-pole squirrel-cage induction motor in laboratory in the case of motor starting; very good agreement has been achieved between the estimated speed and the actually measured speed.